1. Field of the Invention
The present invention relates to a reactor cleaning apparatus which cleans an inner wall surface of a polycrystalline silicon reactor to be used when producing polycrystalline silicon using the Siemens method.
Priority is claimed on Japanese Patent Application No. 2008-014967, filed Jan. 25, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
The Siemens method is known as a method of producing high-purity polycrystalline silicon to be used as a semiconductor material. This Siemens method is a production method of supplying a source gas which is a mixed gas of chlorosilane and hydrogens into contact with a heated silicon seed rod, and depositing the polycrystalline silicon which is generated by the thermal decomposition and hydrogen reducing reaction of a source gas, on the surface of the seed rod. As an apparatus which carries out this production method, a polycrystalline silicon reactor in which many silicon seed rods are erected is used.
When polycrystalline silicon is produced in this polycrystalline silicon reactor, chlorosilane polymers which are generated as a by-product at the time of the thermal decomposition and hydrogen reducing reaction are condensed and adhered on cooled inner wall surface of the reactor. In order to remove the deposited polycrystalline silicon rods, the reactor has to be opened to the atmosphere. On this occasion, chlorosilane polymer and moisture in the atmosphere undergo hydrolysis, hydrogen chloride is generated. The hydrogen chloride erodes the inner surface of the reactor and deteriorates the working environment, and a contamination source is generated the polycrystalline silicon products. Additionally, in the situation that chlorosilane adheres to the bell jar which is a member of the reaction vessel and a bell-shaped object having lower opening edge, reflectivity of inner wall surface of the reactor decreases, the radiation heat from heated silicon rods is not reflected, and the efficiency in the use of electricity decreases. Therefore, in order to generate effectively the highly-pure polycrystalline silicon, when once a reaction is finished, it is necessary to remove the deposits before the next reaction. Therefore, for example, in Japanese Patent Unexamined Publication No. 56-114815, a method of supplying steam inside a wall of a polycrystalline silicon reactor to heat the inner wall surface of the reactor, introducing an humidified gas into the polycrystalline silicon reactor to hydrolyze chlorosilane polymer adhered to the inner wall surface of the reactor, loading a nozzle into the reactor to spray a high-speed jet stream of the inert gas to the inner wall surface and removing the deposits on the inner wall surface of the reactor is suggested. Additionally, the method of removing the deposits by blasting of CO2 pellets to the inner wall surface of the reactor is described, for example, in Japanese Patent Publication No. 3167191.